Foldable display device

ABSTRACT

Provided is a foldable display device. The display device comprises a display panel including a folding area and non-folding areas on both sides of the folding area, a back plate disposed under the display panel, a first support layer disposed under the back plate and having an opening pattern in a portion thereof corresponding to the folding area, and an impact absorbing layer disposed under the first support layer. The impact absorbing layer includes a first portion corresponding to the folding area and a second portion corresponding to the non-folding areas, and a modulus of the first portion is greater than a modulus of the second portion. Accordingly, even when a point impact is applied to the folding area, the point impact is converted into a surface impact, so that damage to the display panel or the touch panel by the point impact can be prevented more effectively. Consequently, impact resistance characteristics of the display device may be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/109,983, filed Dec. 2, 2020, which claims the benefit of KoreanPatent Application No. 10-2019-0163880, filed Dec. 10, 2019, with theKorean Intellectual Property Office, the disclosure of which isincorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to a foldable display device, and moreparticularly, to a foldable display device having improved impactresistance.

Description of the Related Art

Recently, as society advances toward an information-oriented society,the field of display devices for processing and displaying a largeamount of information has rapidly advanced, and various flat displaydevices are being developed correspondingly.

Specific examples of such a flat display device include a liquid crystaldisplay device (LCD), a field emission display device (FED), anelectroluminescence display device (ELD), an organic light emittingdiode (OLED), and the like. These flat display devices exhibit excellentperformance in terms of thinness, weight reduction, and low powerconsumption and thus, are rapidly replacing existing cathode ray tubes(CRT).

Meanwhile, such a flat display device has limitations in reducing aweight and thickness and providing flexibility since it uses a glasssubstrate so as to withstand high heat generated during a manufacturingprocess.

Accordingly, flexible display devices manufactured to maintain displayperformance intact even when they bend like paper, using a flexiblematerial such as plastic or the like, instead of an existing inflexibleglass substrate, are rapidly emerging as next-generation flat displaydevices.

Such flexible display devices may be classified into an unbreakabletype, having high durability by using a plastic thin film transistorsubstrate, instead of glass, a bendable type without being broken, arollable type capable of being rolled up, a foldable type capable ofbeing folded, and the like. These flexible display devices haveadvantages in terms of space use and interior design and can be utilizedin various application fields.

In particular, recently, to realize a large area together with slimness,weight reduction and miniaturization, foldable display devices capableof being portable in a folded state and displaying an image in anunfolded state are being actively studied.

The foldable display devices can be applied not only to mobile devicessuch as mobile phones, ultra-mobile PCs, e-books, and electronicnewspapers, but also be applied to the field of various applications,such as TVs and monitors.

Such a foldable display device includes a display panel for implementingan image, a back plate positioned under the display panel to support thedisplay panel, and a cover window positioned in front of the displaypanel to protect the display panel.

BRIEF SUMMARY

The inventors of the present disclosure have appreciated that due to thestructures and operations of the foldable display device, the display iscapable of being folded and unfolded, and all of the back plate, thecover window, the display panel, are configured in a very thin filmform. Further, such thin film form transmits most of the impactstransmitted from the outside, vertically. The inventors have realizedthat as the cover window and the back plate are in a thin film form,when an impact is applied from the outside to the cover window or backplate, the impact applied from the outside is transmitted directly tothe display panel positioned between the cover window and the backplate. This, in turn, causes damage to the display panel, therebydegrading display quality of the display panel.

The inventors have come up with various structures for reducingresistance. For example, one or more embodiments of the presentdisclosure provides a foldable display device having improved impactresistance.

Further embodiments of the present disclosure provides a foldabledisplay device capable of preventing degradation in display quality.

Technical benefits of the present disclosure are not limited to theabove-mentioned benefits, and other benefits, which are not mentionedabove, can be clearly understood by those skilled in the art from thefollowing descriptions.

According to an aspect of the present disclosure, a foldable displaydevice may include a display panel including a folding area andnon-folding areas on both sides of the folding area. A back plate may bedisposed under the display panel, and a first support layer is disposedunder the back plate and has an opening pattern in a portion thereofcorresponding to the folding area. An impact absorbing layer may bedisposed under the first support layer. The impact absorbing layer mayinclude a first portion corresponding to the folding area and a secondportion corresponding to the non-folding areas, and a modulus of thefirst portion may be greater than a modulus of the second portion.

Other detailed matters of the embodiments are included in the detaileddescription and the drawings.

In the foldable display device according to an embodiment of the presentdisclosure, the first portion of the impact absorbing layercorresponding to the folding area of the display panel is formed of amaterial having a high modulus. Accordingly, even when a point impact isapplied to the folding area, the point impact is converted into asurface impact, so that damage to the display panel or the touch panelby the point impact can be prevented more effectively. Consequently,impact resistance characteristics of the display device may be improved.

Since the technical problems to be solved, the problem-solving means,and the effects described in the specification are not intended to limitthe essential features of the claims. Accordingly, the scope of theclaims is not limited by the contents described in the specification.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic cross-sectional view of a foldable display deviceof the present disclosure;

FIG. 2 is a schematic cross-sectional view of a display panel of FIG. 1;

FIG. 3 is a schematic cross-sectional view of a foldable display deviceaccording to an embodiment of the present disclosure;

FIG. 4 is a photograph showing a ball drop test result of the foldabledisplay device according to an embodiment of the present disclosure; and

FIG. 5 is a schematic cross-sectional view of a foldable display deviceaccording to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Advantages and characteristics of the present disclosure and a method ofachieving the advantages and characteristics will be clear by referringto embodiments described below in detail together with the accompanyingdrawings. However, the present disclosure is not limited to theembodiments disclosed herein but will be implemented in various forms.The embodiments are provided by way of example only so that thoseskilled in the art can fully understand the disclosures of the presentdisclosure and the scope of the present disclosure.

The shapes, sizes, ratios, angles, numbers, and the like illustrated inthe accompanying drawings for describing the embodiments of the presentdisclosure are merely examples, and the present disclosure is notlimited thereto. Like reference numerals generally denote like elementsthroughout the specification. Further, in the following description ofthe present disclosure, a detailed explanation of known relatedtechnologies may be omitted to avoid unnecessarily obscuring the subjectmatter of the present disclosure. The terms such as “including,”“having” used herein are generally intended to allow other components tobe added unless the terms are used with the term “only.” Any referencesto singular may include plural unless expressly stated otherwise.

Components are interpreted to include an ordinary error range even ifnot expressly stated.

When the position relation between two parts is described using theterms such as “on,” “above,” “below,” and “next,” one or more parts maybe positioned between the two parts unless the terms are used with theterm “immediately” or “directly.”

When an element or layer is disposed “on” another element or layer,another layer or another element may be interposed directly on the otherelement or therebetween.

Although the terms “first,” “second,” and the like are used fordescribing various components, these components are not confined bythese terms. These terms are merely used for distinguishing onecomponent from the other components. Therefore, a first component to bementioned below may be a second component in a technical concept of thepresent disclosure.

Like reference numerals generally denote like elements throughout thespecification.

A size and a thickness of each component illustrated in the drawing areillustrated for convenience of description, and the present disclosureis not limited to the size and the thickness of the componentillustrated.

The features of various embodiments of the present disclosure can bepartially or entirely adhered to or combined with each other and can beinterlocked and operated in technically various ways, and theembodiments can be carried out independently of or in association witheach other.

Hereinafter, a display device according to embodiments of the presentdisclosure will be described in detail with reference to accompanyingdrawings.

FIG. 1 is a schematic cross-sectional view of a foldable display deviceaccording to a first embodiment of the present disclosure. FIG. 2 is aschematic cross-sectional view of a display panel of FIG. 1 .

As illustrated, a foldable display device 100 includes a display panel110 for implementing an image, a touch panel 120 including a touchsensor (not shown), a cover window 130 for protecting the display panel110, a back plate 140 for supporting the display panel 110, a firstsupport layer 160 disposed under the back plate 140 and having anopening pattern 161, and a second support layer 150 between the backplate 140 and the first support layer 160.

At this time, when defining directions in drawings for convenience ofexplanation, based on the premise that a display surface of the displaypanel 110 faces frontward, the back plate 140, the first support layer160, and the second support layer 150 are positioned in the rear of thedisplay panel 110, and the cover window 130 is positioned in front ofthe display panel 110.

The touch panel 120 is positioned between the display panel 110 and thecover window 130. The respective components adhere and are attached toone another through adhesives 180 a, 180 b, 190 a, 190 b.

Here, the display panel 110 may be formed of one of a liquid crystaldisplay device (LCD), a field emission display device (FED), anelectroluminescence display device (ELD), and an organic light emittingdiode (OLED), but it is preferable to use the OLED, which is arepresentative of a flexible display device that can maintain displayperformance intact even when it bends like paper.

The OLED is a self-light emitting device and can be manufactured to belight and thin since it does not require a backlight used in a liquidcrystal display device, which is a non-light emitting device.

In addition, the OLED has a viewing angle and a contrast ratio superiorto those of the liquid crystal display device, and is advantageous interms of power consumption, DC low voltage driving and a fast responsespeed. Further, since internal components of the OLED are solid, theOLED is resistant to external impacts and has a wide use temperaturerange.

In particular, since a manufacturing process of the OLED is simple,there is an advantage of reducing a production cost more than that of anexisting liquid crystal display device.

In the display panel 110 formed of such an OLED, a substrate 101 onwhich a driving thin film transistor 102 and a light emitting element103 are formed is encapsulated by an encapsulation part 105 g.

Here, with reference to FIG. 2 , the display panel formed of the OLED(hereinafter, referred to as an OLED panel) will be described in detail.

With reference to FIG. 2 , the substrate 101 serves to support andprotect components of the foldable display device 100 disposed thereon.

Recently, the flexible substrate 101 may be formed of a ductile materialhaving flexible characteristics such as plastic.

The flexible substrate 101 may be in a form of film including one of apolyester-based polymer, a silicone-based polymer, an acrylic-basedpolymer, a polyolefin-based polymer, and a copolymer thereof.

For example, the flexible substrate 101 may be formed of at least one ofpolyethylene terephthalate (PET), polybutylene terephthalate (PBT),polysilane, polysiloxane, polysilazane, polycarbosilane, polyacrylate,polymethacrylate, polymethylacrylate, polymethylmetacrylate,polyethylacrylate, polyethylmethacrylate, a cyclic olefin copolymer(COC), a cyclic olefin polymer (COP), polyethylene (PE), polypropylene(PP), polyimide (PI), polymethylmethacrylate (PMMA), polystyrene (PS),polyacetal (POM), polyether ether ketone (PEEK), polyestersulfone (PES),polytetrafluoroethylene (PTFE), polyvinylchloride (PVC), polycarbonate(PC), polyvinylidenefluoride (PVDF), a perfluoroalkyl polymer (PFA), astyrene acrylonitrile copolymer (SAN), and combinations thereof.

A buffer layer may be further disposed on the flexible substrate 101.The buffer layer prevents penetration of moisture or other impuritiesfrom the outside through the flexible substrate 101 and may planarize asurface of the flexible substrate 101. The buffer layer is notnecessarily a necessary component, and may not be included depending ona type of the thin film transistor 102 disposed on the flexiblesubstrate 101.

The thin film transistor 102 is disposed on the flexible substrate 101and may include a gate electrode 102 a, a source electrode 102 d, adrain electrode 102 c and a semiconductor layer 102 b.

In this case, the semiconductor layer 102 b may be composed of amorphoussilicon or polycrystalline silicon, but is not limited thereto.Polycrystalline silicon has superior mobility than amorphous silicon andlow energy power consumption and excellent reliability, and thus, may beapplied to a driving thin film transistor within the pixel.

The semiconductor layer 102 b may be formed of an oxide semiconductor.The oxide semiconductor has excellent mobility and uniformityproperties. The oxide semiconductor may be formed of a quaternary metaloxide such as an indium tin gallium zinc oxide (InSnGaZnO)-basedmaterial, a ternary metal oxide such as an indium gallium zinc oxide(InGaZnO)-based material, an indium tin zinc oxide (InSnZnO)-basedmaterial, an tin gallium zinc oxide (SnGaZnO)-based material, analuminum gallium zinc oxide (AlGaZnO)-based material, an indium aluminumzinc oxide (InAlZnO)-based material, and a tin aluminum zinc oxide(SnAlZnO)-based material, or a binary metal oxide such as an indium zincoxide (InZnO)-based material, a tin zinc oxide (SnZnO)-based material,an aluminum zinc oxide (AlZnO)-based material, a zinc magnesium oxide(ZnMgO)-based material, a tin magnesium oxide (SnMgO)-based material, anindium magnesium oxide (InMgO)-based material, an indium gallium oxide(InGaO)-based material, an indium oxide (InO)-based material, a tinoxide (SnO)-based material, and a zinc oxide (ZnO)-based material.Composition ratios of respective elements included in the oxidesemiconductor are not limited.

The semiconductor layer 102 b may include a source region including ap-type or n-type impurity, a drain region, and a channel region betweenthe source region and the drain region. The semiconductor layer 102 bmay further include a low concentration doped region between the sourceregion and the drain region adjacent to the channel region.

The source region and the drain region are doped with a highconcentration of impurity, and may be connected to the source electrode102 d and the drain electrode 102 c of the thin film transistor 102,respectively.

As an impurity ion, the p-type impurity or n-type impurity may be used.The p-type impurity may be one of boron (B), aluminum (Al), gallium(Ga), and indium (In), and the n-type impurity may be one of phosphorus(P), arsenic (As), and antimony (Sb).

The channel region of the semiconductor layer 102 b may be doped withthe n-type impurity or p-type impurity according to an NMOS or PMOS thinfilm transistor structure, and the thin film transistor included in thefoldable display device 100 according to an embodiment of the presentdisclosure may be an NMOS or PMOS thin film transistor.

A first insulating layer 105 a is an insulating layer composed of asingle layer of silicon oxide (SiOx) or silicon nitride (SiNx) ormultiple layers thereof, and may be disposed such that a current flowingthrough the semiconductor layer 102 b does not flow to the gateelectrode 102 a. In addition, silicon oxide is less ductile than metal,but is superior in ductility to silicon nitride, and may be formed as asingle layer or multiple layers depending on characteristics thereof.

The gate electrode 102 a serves as a switch for turning on or turningoff the thin film transistor 102 based on an electric signal transmittedfrom the outside through the gate line, and may be composed of a singlelayer or multiple layers of a conductive metal such as copper (Cu),aluminum (Al), molybdenum (Mo), chromium (Cr), gold (Au), titanium (Ti),nickel (Ni), and neodymium (Nd), or alloys thereof. However, embodimentsare not limited thereto.

The source electrode 102 d and the drain electrode 102 c are connectedto the data line, and may enable an electric signal transmitted from theoutside to be transmitted from the thin film transistor 102 to the lightemitting element 103. The source electrode 102 d and the drain electrode102 c may be composed of a single layer or multiple layers of aconductive metal such as copper (Cu), aluminum (Al), molybdenum (Mo),chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), and neodymium(Nd), or alloys thereof, but are not limited thereto.

To insulate the gate electrode 102 a and the source electrode 102 d andthe drain electrode 102 c from each other, a second insulating layer 105b composed of a single layer or multiple layers of silicon oxide (SiOx)or silicon nitride (SiNx) may be disposed between the gate electrode 102a and the source electrode 102 d and the drain electrode 102 c.

A passivation layer formed of an inorganic insulating layer such assilicon oxide (SiOx) or silicon nitride (SiNx) may be disposed on thethin film transistor 102.

The passivation layer may prevent unnecessary electrical connectionsbetween components disposed over and under the passivation layer andprevent contamination or damage from the outside. The passivation layermay be omitted depending on configurations and characteristics of thethin film transistor 102 and the light emitting element 103.

Structures of the thin film transistor 102 may be divided into aninverted-staggered structure and a coplanar structure according topositions of elements constituting the thin film transistor 102. Forexample, the thin film transistor having an inverted-staggered structurerefers to a thin film transistor having a structure in which a gateelectrode is positioned opposite to a source electrode and a drainelectrode based on a semiconductor layer. As in FIG. 2 , the thin filmtransistor 102 having a coplanar structure refers to a thin filmtransistor having a structure in which the gate electrode 102 a ispositioned on the same side as the source electrode 102 d and the drainelectrode 102 c based on the semiconductor layer 102 b.

In FIG. 2 , the thin film transistor 102 having a coplanar structure isillustrated, but the foldable display device 100 according to anembodiment of the present disclosure may also include a thin filmtransistor having an inverted-staggered structure.

For convenience of description, only a driving thin film transistor isillustrated among various thin film transistors that may be included inthe foldable display device 100. A switching thin film transistor, acapacitor, or the like may also be included in the foldable displaydevice 100.

In addition, when a signal is applied from the gate line to theswitching thin film transistor, the switching thin film transistortransmits the signal from the data line to a gate electrode of thedriving thin film transistor. The driving thin film transistor maytransmit a current transferred through power lines to an anode 103 a bythe signal transmitted from the switching thin film transistor, andcontrol light emission by the current transmitted to the anode 103 a.

Planarization layers 105 c and 105 d may be disposed on the thin filmtransistor 102 to protect the thin film transistor 102, to alleviate astep caused by the thin film transistor 102, and to reduce parasiticcapacitance generated between the thin film transistor 102 and the gateline and the data line, and the light emitting elements 103.

The planarization layers 105 c and 105 d may be formed of one or more ofacrylic resin, epoxy resin, phenolic resin, polyamides resin, polyimidesresin, unsaturated polyesters resin, polyphenylene resin, polyphenylenesulfides resin and benzocyclobutene, but are not limited thereto.

The foldable display device 100 according to an embodiment of thepresent disclosure may include a first planarization layer 105 c and asecond planarization layer 105 d that are sequentially stacked. That is,the first planarization layer 105 c may be disposed on the thin filmtransistor 102 and the second planarization layer 105 d may be disposedon the first planarization layer 105 c.

A buffer layer may be disposed on the first planarization layer 105 c.The buffer layer may be composed of multiple layers of silicon oxide(SiOx) to protect components disposed on the first planarization layer105 c, and may be omitted depending on configurations andcharacteristics of the thin film transistor 102 and the light emittingelement 103.

An intermediate electrode 104 may be connected to the thin filmtransistor 102 through a contact hole formed in the first planarizationlayer 105 c. The intermediate electrode 104 is stacked to be connectedto the thin film transistor 102, and the data line may also be formed ina multilayer structure.

The data line may be formed to have a structure in which a lower layerformed of the same material as the source electrode 102 d and the drainelectrode 102 c and an upper layer formed of the same material as theintermediate electrode 104 are connected to each other. That is, thedata line may be implemented in a structure in which two layers areconnected in parallel to each other, and in this case, line resistanceof the data line may be reduced.

Meanwhile, a passivation layer formed of an inorganic insulating layersuch as silicon oxide (SiOx) or silicon nitride (SiNx) may be furtherdisposed on the first planarization layer 105 c and the intermediateelectrode 104. The passivation layer may serve to prevent unnecessaryelectrical connections between components and to prevent contaminationor damage from the outside, and may be omitted depending onconfigurations and characteristics of the thin film transistor 102 andthe light emitting element 103.

The light emitting element 103 disposed on the second planarizationlayer 105 d may include the anode 103 a, a light emitting unit 103 b,and a cathode 103 c.

The anode 103 a may be disposed on the second planarization layer 105 d.

The anode 103 a serves to supply holes to the light emitting unit 103 band is connected to the intermediate electrode 104 through a contacthole in the second planarization layer 105 d to thereby be electricallyconnected to the thin film transistor 102.

The anode 103 a may be formed of a transparent conductive material, suchas indium tin oxide (ITO), indium zinc oxide (IZO), or the like, but isnot limited thereto.

When the foldable display device 100 is a top emission type displaydevice that emits light to an upper portion thereof where the cathode103 c is disposed, it may further include a reflective layer such thatthe emitted light is reflected from the anode 103 a to be smoothlyemitted in a direction toward the upper portion where the cathode 103 cis disposed.

The anode 103 a may be a two-layer structure in which a transparentconductive layer formed of a transparent conductive material and areflective layer are sequentially stacked, or a three-layer structure inwhich a transparent conductive layer, a reflective layer and atransparent conductive layer are sequentially stacked. The reflectivelayer may be formed of silver (Ag) or an alloy including silver.

A bank 105 e disposed on the anode 103 a and the second planarizationlayer 105 d may define sub-pixels by dividing areas that actually emitslight. After forming a photoresist on the anode 103 a, the bank 105 emay be formed by photolithography. Photoresist refers to aphotosensitive resin whose solubility in a developer is changed by theaction of light, and a specific pattern may be obtained by exposing anddeveloping the photoresist. Types of photoresist may be classified intoa positive photoresist and a negative photoresist. The positivephotoresist is a photoresist where solubility of an exposed portionthereof in the developer is increased by exposure. When the positivephotoresist is developed, a pattern from which exposed portions areremoved is obtained. The negative photoresist is a photoresist wheresolubility of the exposed portion thereof in the developer issignificantly lowered by the exposure. When the negative photoresist isdeveloped, a pattern from which non-exposed portions are removed isobtained.

A fine metal mask (FMM) which is a deposition mask, may be used to formthe light emitting unit 103 b of the light emitting element 103.

In addition, to prevent damage that may occur due to contact with thedeposition mask disposed on the bank 105 e and to maintain a constantdistance between the bank 105 e and the deposition mask, a spacer 105 fformed of one of polyimide which is a transparent organic material,photo acryl, and benzocyclobutene (BCB) may be disposed on the bank 105e.

The light emitting unit 103 b may be disposed between the anode 103 aand the cathode 103 c.

The light emitting unit 103 b serves to emit light and may include atleast one of a hole injection layer (HIL), a hole transport layer (HTL),a light emitting layer, an electron transport layer (ETL), and anelectron injection layer (EIL), and some components may be omitteddepending on a structure or characteristics of the foldable displaydevice 100. Here, an electroluminescent layer and an inorganic emittinglayer may be applied to the light emitting layer.

The hole injection layer is disposed on the anode 103 a to facilitate aninjection of holes.

The hole transport layer is disposed on the hole injection layer tosmoothly transport holes to the light emitting layer.

The light emitting layer is disposed on the hole transport layer and mayinclude a material capable of emitting light of a specific color tothereby emit light of a specific color. In addition, a luminescentmaterial may be formed using a phosphorescent material or a fluorescentmaterial.

The electron injection layer may be further disposed on the electrontransport layer. The electron injection layer is an organic layer thatfacilitates an injection of electrons from the cathode 103 c and may beomitted depending on the structure and characteristics of the foldabledisplay device 100.

On the other hand, at a position adjacent to the light emitting layer,an electron blocking layer or a hole blocking layer that blocks a flowof holes or electrons is further disposed to prevent a phenomenon inwhich when electrons are injected into the light emitting layer, theelectrons move from the light emitting layer and pass to the adjacenthole transport layer or a phenomenon in which when holes are injectedinto the light emitting layer, the holes move from the light emittinglayer and pass to the adjacent electron transport layer, so thatluminous efficiency may be improved.

The cathode 103 c is disposed on the light emitting unit 103 b andserves to supply electrons to the light emitting unit 103 b. Since thecathode 103 c needs to supply electrons, it may be formed of a metalmaterial such as magnesium (Mg), silver-magnesium (Ag:Mg), which is aconductive material having a low work function, and is not limitedthereto.

When the foldable display device 100 is a top emission type displaydevice, the cathode 103 c may be a transparent conductive oxide such asindium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide(ITZO), zinc oxide (ZnO), and tin oxide (TO).

The encapsulation part 105 g may be disposed on the light emittingelement 103 to prevent the thin film transistor 102 and the lightemitting element 103, which are components of the foldable displaydevice 100, from being oxidized or damaged due to moisture, oxygen, orimpurities introduced from the outside. The encapsulation part 105 g maybe formed by stacking a plurality of encapsulation layers, a foreignmaterial compensation layer, and a plurality of barrier films.

The encapsulation layer may be disposed on the entire surface of anupper portion of the thin film transistor 102 and the light emittingelement 103, and may be formed of one of silicon nitride (SiNx) oraluminum oxide (AlyOz) which is an inorganic material. However,embodiments are not limited thereto. An encapsulation layer may befurther disposed on the foreign material compensation layer disposed onthe encapsulation layer.

The foreign material compensation layer is disposed on the encapsulationlayer, and an organic material such as silicon oxycarbon (SiOCz),acrylic (acryl), or epoxy-based resin may be used for the foreignmaterial compensation layer. However, embodiments are not limitedthereto. When a defect occurs due to a crack generated by a foreignmaterial or particles that may be generated during a process, it may becompensated for by covering a curve and a foreign material by theforeign material compensation layer.

A barrier film may be disposed on the encapsulation layer and theforeign material compensation layer, whereby the foldable display device100 may delay the penetration of oxygen and moisture from the outside.The barrier film is configured in the form of a light-transmissive anddouble-sided adhesive film, and may be composed of any one ofolefin-based, acrylic-based, and silicon-based insulating materials.Alternatively, a barrier film composed of any one of COP (cycloolefinpolymer), COC (cycloolefin copolymer) and PC (Polycarbonate) may befurther stacked, but is not limited thereto.

FIG. 3 is a schematic cross-sectional view of a foldable display deviceaccording to an embodiment of the present disclosure.

Some components in FIG. 3 are substantially the same as and similar tothose described in FIG. 1 and thus, descriptions thereof will beomitted.

A back plate 240, a second support layer 250, a first support layer 260,and an impact absorbing layer 270 are sequentially disposed on a rearsurface of the display panel 210, and a cover window 230 is located infront of the display panel 210. In addition, a touch panel 220 ispositioned between the display panel 210 and the cover window 230. Therespective components adhere and are attached to one another throughadhesives 280 a, 280 b, 290 a, 290 b, 290 c.

The back plate 240 is attached to the rear surface of the display panel210 to support the display panel 210 since a substrate 101 of thedisplay panel 210 is too thin. The back plate 240 may be formed of ametal material such as stainless steel (SUS) or a polymer such aspolymethylmetacrylate (PMMA), polycarbonate (PC), polyvinylalcohol(PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate(PET), silicone, or polyurethane (PU).

The first support layer 260 is also referred to as a plate bottom. Thefirst support layer 260 may include an opening pattern 261 in a portionthereof corresponding to a folding area FA of a foldable display device200. An elastic deformation region is increased by the opening pattern261 formed in the folding area FA, thereby allowing for restoration. Insome embodiments, the opening pattern 261 is an open, void area (e.g.,filled with air). In other embodiments, the opening pattern 261 is avoid area filled with any suitable materials so that the opening pattern261 serves as a spring, so that elastic restoration energy increases,thereby allowing for a reduction in restoration time. Therefore, foldingcharacteristics of the foldable display device 200 may be improved. Inaddition, the first support layer 260 may serve to prevent transfercaused by a set. The first support layer 260 is formed of a metalmaterial such as stainless steel (SUS), but is not limited thereto. Thefirst support layer 260 may also be formed of a polymer such aspolymethylmetacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol(PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate(PET), silicone, or polyurethane (PU).

The second support layer 250 is also referred to as a plate top. Thesecond support layer 250 is disposed between the back plate 240 and thefirst support layer 260 and can enhance rigidity of the display panel210. Further, the second support layer 250 may function to prevent theopening pattern 261 from being viewed through the display panel. Thesecond support layer 250 may be formed of a metal material such asstainless steel (SUS) which includes iron (Fe) or other metals, forexample, chromium (Cr) and nickel (Ni) contained in the iron, aluminum(Al), or magnesium (Mg), but is not limited thereto. The second supportlayer 250 may be formed of a polymer such as polymethylmetacrylate(PMMA), polycarbonate (PC), polyvinyl alcohol (PVA),acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET),silicone, or polyurethane (PU).

As described above, since a foldable display device should be able to befolded and unfolded, all of a back plate and a cover window, as well asa display panel, are configured in a very thin film form, and such athin film form transmits most of impacts transmitted from the outside,vertically.

For example, when an impact is transmitted from the outside to the coverwindow, the impact transmitted to the cover window is transmitted to atouch panel or the display panel positioned under the cover window.

Thus, electrodes of a touch sensor of the touch panel or elements of thedisplay panel are damaged. Accordingly, the inventors have invented anew structure of a foldable display device to solve limitationsdescribed above.

The impact absorbing layer 270 may be disposed under the first supportlayer 260. The impact absorbing layer 270 may minimize transmission ofimpacts which are applied from the outside to the touch panel or thedisplay panel 210. The impact absorbing layer 270 may be formed ofsilicone, silicone foam, acrylic foam, polypropylene foam, polyurethane(PU), polyurethane foam, or thermoplastic polyurethane (TPU), but is notlimited thereto.

Here, the impact absorbing layer 270 has a thickness of 100 μm to 1000μm. When the impact absorbing layer has a thickness of less than 100 μm,impact absorption capacity is insignificant, and when the impactabsorbing layer has a thickness of greater than 1000 μm, it may causedifficulties in folding the foldable display device.

However, the inventors have found a vulnerability in the structure asdescribed above. FIG. 4 is a photograph showing a ball drop test resultof the foldable display device of FIG. 3 . With reference to FIG. 4 , itcan be seen that the folding area FA of the display panel 210 wasdamaged due to point impacts. The point impact which is an impactexerted on a local region may apply stronger damage to the displaypanel, than that of a surface impact applied to the entire surface.

When a point impact is applied from the outside, the point impact isconverted into a surface impact in a non-folding area of the firstsupport layer, having no opening pattern, so that the impact can beabsorbed well. However, since the opening pattern is present in afolding area of the first support layer to improve foldingcharacteristics, when a point impact is applied to an upper portion ofthe folding area, it cannot be converted into a surface impact, causingdamage to the display panel or the touch panel. Accordingly, theinventors have recognized this problem and invented a new structure ofthe impact absorbing layer.

FIG. 5 is a cross-sectional view schematically illustrating a foldabledisplay device 300 according to another embodiment of the presentdisclosure.

With reference to FIG. 5 , the foldable display device 300 according toanother embodiment of the present disclosure may include a display panel310. A cover window 330 is located in front of the display panel 310. Inaddition, a touch panel 320 is positioned between the display panel 310and the cover window 330. The display panel 310 may include a foldingarea FA and non-folding areas NFA on both sides of the folding area FA.A back plate 340 is disposed under the display panel 310. A firstsupport layer 360 having an opening pattern 361 in a portion thereofcorresponding to the folding area FA is disposed under the back plate340. An impact absorbing layer 370 is disposed under the first supportlayer 360. The impact absorbing layer 370 includes a first portion 370-1corresponding to the folding area FA and a second portion 370-2corresponding to the non-folding areas NFA. The impact absorbing layer370 may be formed of a material in which a modulus of the first portion370-1 is higher than that of the second portion 370-2. That is, thefirst portion 370-1 may be formed of a material having a modulus ofelasticity greater than that of the second portion 370-2. The respectivecomponents adhere and are attached to one another through adhesives 380a, 380 b, 390 a, 390 b, 390 c.

The first portion 370-1 may be formed of at least one of silicone,silicone foam, acrylic foam, polypropylene foam, polyurethane (PU),polyurethane foam, and thermoplastic polyurethane (TPU).

The first portion 370-1 has a modulus value of 1 MPa to 30 MPa, and thefirst portion 370-1 has a thickness of 100 μm to 1000 μm. When the firstportion 370-1 has a thickness of less than 100 μm, impact absorptioncapacity is insignificant, and when the first portion 370-1 has athickness of greater than 1000 μm, it may cause difficulties in foldingthe foldable display device 300.

The second portion 370-2 may be formed of at least one of silicone,silicone foam, acrylic foam, polypropylene foam, polyurethane (PU),polyurethane foam, and thermoplastic polyurethane (TPU).

The second portion 370-2 has a modulus value of 10 KPa to 1000 KPa, andthe second portion 370-2 has a thickness of 100 μm to 1000 μm. When thesecond portion 370-2 has a thickness of less than 100 μm, impactabsorption capacity is insignificant, and when the second portion 370-2has a thickness of greater than 1000 μm, it may cause difficulties infolding the foldable display device 300.

TABLE 1 First Support Layer Impact Opening Pattern Opening PatternAbsorbing Layer (present) (not present) None 2.5 cm 2.5 cm 4 MPa 12.5 cm2.5 cm 10 MPa 10 cm 2.5 cm 10 KPa 2.5 cm 15 cm 20 KPa 2.5 cm 15 cm

Table 1 above shows ball drop test results indicating heights of pointsin time at which damage to the display panel occurred according to themodulus of the impact absorbing layer 370 and the presence or absence ofthe opening pattern of the first support layer 360. With reference toTable 1 above, in a case in which the modulus of the first portion 370-1having the opening pattern 361 was relatively high (4 MPa or 10 MPa),when a ball was dropped, it can be confirmed that a height at whichdamage to the display panel 310 occurred was 10 cm or more. However, ina case in which the modulus of the first portion 370-1 having theopening pattern 361 was relatively low (10 KPa or 20 KPa), it can beconfirmed that damage to the display panel 310 occurred when the ballwas dropped at a height of 2.5 cm. On the other hand, when the modulusof the second portion 370-2 having no opening pattern 361 was relativelyhigh (4 MPa or 10 MPa), damage to the display panel 310 occurred whenthe ball was dropped at a height of 2.5 cm. However, when the modulus ofthe second portion 370-2 having no opening pattern 361 was relativelylow (10 KPa or 20 KPa), it can be confirmed that damage to the displaypanel 310 occurred when the ball was dropped at a height of 15 cm.

Through this, in the foldable display device 300 according to theembodiment of the present disclosure, the impact absorbing layer 370 isdisposed such that the modulus of the first portion 370-1 of the impactabsorbing layer 370 corresponding to the folding area FA has arelatively large value (1 to 30 MPa) and the modulus of the secondportion 370-2 of the impact absorbing layer 370 corresponding to thenon-folding area NFA has a value smaller than the modulus of the firstportion 370-1. Thus, as compared to a general foldable display device,even when an external impact is applied to the foldable display device300, the impact is partially alleviated to thereby improve impactresistance characteristics of the touch panel 320 or the display panel310.

A second support layer 350 may be further included between the backplate 340 and the first support layer 360. The second support layer 350may enhance rigidity of the display panel 310. Further, the secondsupport layer 250 may function to prevent the opening pattern 361 frombeing viewed through the display panel 310.

The second support layer 350 may be formed of a metal material such asstainless steel (SUS) which includes iron (Fe) or other metals, forexample, chromium (Cr) and nickel (Ni) contained in the iron, aluminum(Al), or magnesium (Mg), but is not limited thereto. The second supportlayer 350 may be formed of a polymer such as polymethylmetacrylate(PMMA), polycarbonate (PC), polyvinyl alcohol (PVA),acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET),silicone, or polyurethane (PU).

Meanwhile, in the description so far, it is described and illustratedthat the touch panel 320 is located over the display panel 310 on whichan image is implemented, in the foldable display device 300. However, inother embodiments, the touch panel 320 can be omitted.

The foldable display device 300 according to another embodiment of thepresent disclosure may include the display panel 310. The display panel310 may include the folding area FA and the non-folding areas NFA onboth sides of the folding area FA. The first support layer 360 havingthe opening pattern 361 in a portion thereof corresponding to thefolding area FA may be under the display panel 310. The impact absorbinglayer 370 is disposed under the first support layer 360. The impactabsorbing layer 370 includes the first portion 370-1 corresponding tothe folding area FA and the second portion 370-2 corresponding to thenon-folding areas NFA. In the impact absorbing layer 370, the modulus ofthe first portion 370-1 has a value greater than that of the secondportion 370-2 to reduce damage to the display panel 310 caused by apoint impact applied to the folding area FA.

The first portion 370-1 may convert the point impact applied to thefolding area FA of the display panel 310 into a surface impact toprevent shape deformation of the folding area FA. The opening pattern361 is not formed in the first support layer 360 corresponding to thesecond portion 370-2. Therefore, the first support layer 360 can converta point impact applied from the outside into a surface impact. However,since the opening pattern 361 is formed in the first support layer 360corresponding to the first portion 370-1 so as to improve foldingcharacteristics, the point impact cannot be converted into a surfaceimpact due to the opening pattern 361. Accordingly, the first portion370-1 corresponding to the opening pattern 361 has a high modulus valuein order to convert the point impact into a surface impact. That is, thefirst portion 370-1 may be formed of a material having a modulus ofelasticity greater than that of the second portion 370-2.

The first portion 370-1 may be formed of at least one of silicone,silicone foam, acrylic foam, polypropylene foam, polyurethane (PU),polyurethane foam, and thermoplastic polyurethane (TPU).

The first portion 370-1 has a modulus value of 1 to 30 MPa, and thefirst portion 370-1 has a thickness of 100 to 1000 μm. When the firstportion 370-1 has a thickness of less than 100 μm, impact absorptioncapacity is insignificant, and when the first portion 370-1 has athickness of greater than 1000 μm, it may cause difficulties in foldingthe foldable display device 300.

The second portion 370-2 may be formed of at least one of silicone,silicone foam, acrylic foam, polypropylene foam, polyurethane (PU),polyurethane foam, and thermoplastic polyurethane (TPU).

The second portion 370-2 has a modulus value of 10 KPa to 1000 KPa, andthe second portion 370-2 has a thickness of 100 μm to 1000 μm. When thesecond portion 370-2 has a thickness of less than 100 μm, impactabsorption capacity is insignificant, and when the second portion 370-2has a thickness of greater than 1000 μm, it may cause difficulties infolding the foldable display device 300.

In the foldable display device 300 according to an embodiment of thepresent disclosure, the first portion 370-1 of the impact absorbinglayer 370 corresponding to the folding area FA of the display panel 310is formed of a material having a high modulus. Thus, even when a pointimpact is applied to the folding area FA, the point impact is convertedinto a surface impact, so that damage to the display panel 310 or thetouch panel 320 by the point impact can be prevented more effectively.Consequently, impact resistance characteristics of the display device300 may be improved.

Although the embodiments of the present disclosure have been describedin detail with reference to the accompanying drawings, the presentdisclosure is not limited thereto and may be embodied in many differentforms without departing from the technical concept of the presentdisclosure. Therefore, the embodiments of the present disclosure areprovided for illustrative purposes only but not intended to limit thetechnical concept of the present disclosure. The scope of the technicalconcept of the present disclosure is not limited thereto. Therefore, itshould be understood that the above-described embodiments areillustrative in all aspects and do not limit the present disclosure. Theprotective scope of the present disclosure should be construed based onthe following claims, and all the technical concepts in the equivalentscope thereof should be construed as falling within the scope of thepresent disclosure.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A foldable display device, comprising: adisplay panel including a folding area and non-folding areas on bothsides of the folding area; a back plate disposed under the displaypanel; a first support layer disposed under the back plate; and anopening pattern arranged in a portion corresponding to the folding area,the opening pattern extending through the first support layer, andwherein the display panel includes: a flexible substrate; a thin filmtransistor disposed on the flexible substrate, the thin film transistorincluding a gate electrode, source electrode, a drain electrode, and asemiconductor layer; a first planarization layer on the thin filmtransistor; a second planarization layer sequentially stacked on thefirst planarization layer; a light emitting element disposed on thesecond planarization layer, the light emitting element including ananode, a light emitting unit, and a cathode; and an intermediateelectrode on the first planarization layer, the intermediate electrodecoupled to the drain electrode of the thin film transistor through acontact hole formed in the first planarization layer and coupled to theanode through a contact hole in the second planarization layer.
 2. Thefoldable display device of claim 1, further comprising: a bank disposedon the anode and the insulating layer and dividing areas that emitslight; and a spacer disposed on the bank and formed of a transparentorganic material.
 3. The foldable display device of claim 1, furthercomprising: a cover window positioned in front of the display panel; atouch panel positioned between the display panel and the cover window;and a second support layer between the back plate and the first supportlayer.
 4. The foldable display device of claim 3, further comprising: aplurality of adhesives attached at least one of the cover window, thetouch panel, the display panel, the back plate, the second supportlayer, and the first support layer.
 5. The foldable display device ofclaim 3, wherein the plurality of adhesives includes a first adhesivedisposed between the cover window and the touch panel, a second adhesivedisposed between the display panel and the back plate, a third adhesivedisposed between the back plate and the second support layer, and aforth adhesive disposed between the second support layer and the firstsupport layer.
 6. The foldable display device of claim 1, wherein thedisplay panel further includes an encapsulation part disposed on thelight emitting element, wherein, in operation, the encapsulation partprevents the thin film transistor and the light emitting element frombeing oxidized or damaged due to moisture.
 7. The foldable displaydevice of claim 6, further comprising touch sensor having electrodesdisposed on the encapsulation part.
 8. The foldable display device ofclaim 1, further comprising: an impact absorbing layer disposed underthe first support layer, wherein the impact absorbing layer includes afirst portion corresponding to the folding area and a second portioncorresponding to the non-folding areas, wherein a modulus of the firstportion is greater than a modulus of the second portion.
 9. The foldabledisplay device of claim 8, wherein the first portion is formed of amaterial having a modulus of elasticity greater than that of the secondportion.
 10. The foldable display device of claim 8, wherein the firstportion and the second portion includes any one of materials selectedfrom silicone, silicone foam, acrylic foam, polypropylene foam,polyurethane, polyurethane foam, or thermoplastic polyurethane.
 11. Thefoldable display device of claim 8, wherein the first portion has athickness of 100 to 1000 μm and a modulus of 1 to 30 MPa.
 12. Thefoldable display device of claim 11, wherein the second portion has athickness of 100 to 1000 μm and a modulus of 10 to 1000 KPa.
 13. Afoldable display device, comprising: a display panel including a foldingarea and non-folding areas on both sides of the folding area; a backplate disposed under the display panel; a first support layer disposedunder the back plate; and an opening pattern included in the firstsupport layer, the opening pattern arranged in a portion correspondingto the folding area, wherein the back plate and the first support layerare spaced apart from each other, and wherein the display panelincludes: a flexible substrate; a thin film transistor disposed on theflexible substrate, the thin film transistor including a gate electrode,source electrode, a drain electrode, and a semiconductor layer; a firstplanarization layer on the thin film transistor; a second planarizationlayer sequentially stacked on the first planarization layer; a lightemitting element disposed on the second planarization layer, the lightemitting element including an anode, a light emitting unit, and acathode; and an intermediate electrode on the first planarization layer,the intermediate electrode coupled to the drain electrode of the thinfilm transistor through a contact hole formed in the first planarizationlayer and coupled to the anode through a contact hole in the secondplanarization layer.
 14. The foldable display device of claim 13,further comprising: a cover window positioned in front of the displaypanel; a touch panel positioned between the display panel and the coverwindow; and a second support layer between the back plate and the firstsupport layer.
 15. The foldable display device of claim 13, wherein thedisplay panel further includes an encapsulation part disposed on a lightemitting element, wherein, in operation, the encapsulation part preventsa thin film transistor and the light emitting element in the displaypanel from being oxidized or damaged due to moisture.
 16. The foldabledisplay device of claim 13, further comprising: an impact absorbinglayer disposed under the first support layer, wherein the impactabsorbing layer includes a first portion corresponding to the foldingarea and a second portion corresponding to the non-folding areas,wherein a modulus of the first portion is greater than a modulus of thesecond portion.
 17. The foldable display device of claim 16, wherein thefirst portion is formed of a material having a modulus of elasticitygreater than that of the second portion.
 18. The foldable display deviceof claim 16, wherein the first portion and the second portion includesany one of materials selected from silicone, silicone foam, acrylicfoam, polypropylene foam, polyurethane, polyurethane foam, orthermoplastic polyurethane.